1. FIELD OF THE INVENTION
The invention relates to a method and apparatus for sealing of a casing in a subterranean well, and particularly to a method employing an inflatable packer on the bottom of the casing which is filled with inflation fluid to expand into sealing engagement with the well bore.
2. SUMMARY OF THE PRIOR ART
The cementing of casings in subterranean wells is a time honored procedure. In many cases, the drilled well bore extends downwardly a substantial distance beyond the region of the well for which a casing is required. Due to the high cost of casing, it would be highly desirable to utilize a casing string having a length just sufficient to reach the desired area of the well and not extending to the bottom of the well bore. Inflatable packers have been utilized in the past to accomplish this objective and have been filled with inflation fluid, such as cementing fluid in order to provide an inflation fluid barrier between the bottom end of the casing string and the well bore. After installation of the inflatable packer, cement is applied by conventional apparatus to surround the upper portions of the casing string.
The fluid supply conduits heretofore employed for introducing inflation fluid into the inflatable packer have been characterized by significantly small flow areas, thus increasing the time for the cementing operation and providing an environment where a portion of the flow path might be readily plugged by the cementing fluid before the inflatable packer is completely filled.
Since cementing or other inflation fluid has to be supplied to the inflatable packer through the casing bore, special valving apparatus is required to first, prevent well fluid from entering the inflatable packer during run-in; secondly, to open a passage for flow of cementing fluid into the inflatable packer; thirdly, to seal off the aforementioned fluid passage in response to the expansion and filling of the inflatable packer; and lastly, to permanently close any ports in the casing wall required for the passage of cementing or other inflation fluid into the inflatable packer. A method and apparatus for automatically conditioning the fluid supply conduits for the inflatable packer to accomplish the aforedescribed operations in sequence has not been available in the prior art.